The present invention relates to loudspeaker enclosures of the low frequency exponential folded horn type. More specifically, it relates to front-loaded horn enclosures that are reflex-ported and are intended for use in close proximity to at least one planar surface, such as a floor, ceiling or wall.
The current invention relates directly to my previous U.S. patent application Ser. No. 11/107,453 and can be considered a contribution over my previous invention with regard to improved low frequency performance by increasing the available back chamber volume with minimal changes to the overall dimensions of the previous invention, and an improvement in comparatively reducing construction costs.
The current invention provides improved economic benefits by simplifying the construction process compared to the previous invention by increasing the number of parts employed which would seem counter-intuitive, however, the parts in question are relatively simple to manufacture, and provide for simplified construction methods, thereby resulting in less time and effort being required.
The current invention is designed around a specific 15-inch purpose-built driver which provides the opportunity to utilize a relatively small horn throat cross-section as required for the maximum mid-band efficiency of the driver and to further optimize the low frequency performance specific to the driver. The requirements of the particular driver and the constraints imposed on the current invention are defined as follows:                a) Maximum Throat Cross-Sectional Area (St)=58.5 square inches        b) Port Tuning below the Low Frequency Cutoff (Fc) of the horn (approximately 70 Hz)        c) Driver capable of resonant behavior in approximately 4 cubic feet of back chamber volume (Vb) to capacitate the port        d) Enclosure footprint size to remain within +/−1 inch in width or length of the previously cited prior art; vertical height remains unchanged        
The current invention substantially maintains the overall footprint of the previous invention, and the overall cabinet dimensions remain very close to the previous design, in the present disclosure, within an inch of the dimensions of the previous invention. Increases to the throat cross-sectional area (St) would impact on the overall enclosure size unless the back chamber volume (Vb) is made smaller to compensate. The balance of the two is determined by the performance characteristics of the driver selected, and the otherwise arbitrary size limitations imposed on the enclosure. In the current invention, the overall size of the enclosure is limited to within +1 inch of the previous invention in any dimension. The overall size of the previously cited prior art was deemed suitably compact considering its response capabilities and provides the size constraints imposed on the current invention.
The current invention, while specific to a particular driver, is more economical to build and increases the potential low frequency performance capabilities afforded by the available increased back chamber volume compared to the previously cited prior art invention.